Natural gas is, in many cases, the fuel of choice for firing gas turbines because of its lower cost and desirable combustion characteristics as compared with alternative fuels. Many combustion turbines, though, have the capability to fire either natural gas or a liquid fuel, including various grades of diesel fuel, such as No. 2 diesel fuel, depending on cost, availability and desired combustion characteristics. In many cases the liquid fuel system is used primarily as a backup system. As an example, current Dry Low NOX (DLN) combustors generally utilize a backup liquid fuel system. In other cases, gas turbine sites seasonally operate on liquid fuel due to the lower cost or enhanced availability of the liquid fuel.
While liquid fuel systems are desirable, either as a backup or alternate fueling system, their operating and maintenance costs are currently prohibitive. Atomizing air is frequently used to provide atomization of the liquid fuel to obtain desirable combustion characteristics, including improved emissions and turbine performance. Atomizing air systems require bleeding compressor air and using pumps to raise the air pressure to a level sufficient for liquid fuel atomization. They impose additional capital equipment and maintenance costs and reduce turbine and power plant efficiency. Thus, elimination of atomizing air systems is desirable to reduce capital equipment and maintenance costs, reduce system complexity and improve the power plant reliability and heat rate.
Therefore, improved liquid fueling systems and fueling methods that avoid the disadvantages described above are desirable.